O'Mahony conjured his match-defining tackle from nowhere to drag Furno's foot into touch as he dotted down - only to hand Ireland a frenzied finish after a cheap yellow card.

Keith Earls set a new Ireland record with his eighth World Cup try, but Ireland could not pull away, hounded at every turn by the dogged and fiercely physical Italians.

Spurred on by the return of their fit-again spiritual leader Sergio Parisse, the Azzurri conspired to spoil Ireland's day at London's Olympic Stadium.

Combative Munster flanker O'Mahony was sin-binned with nine nervy minutes to play for charging shoulder-first into a ruck, with Italy just a converted try behind.

Ireland held on however, buoyed by what was effectively a home crowd. Head coach Schmidt's men failed to fire however, and must raise the level markedly in order to beat France next weekend.

Ireland face Les Bleus in Cardiff to fight out top spot in Pool D, with the winners likely to take on Argentina in the last eight.

Schmidt's side dominated neither territory nor possession in the first-half, and yet still created several chances they could not convert.

Johnny Sexton bisected Italy's line with ease before slotting the opening points from the tee, though Italy then levelled through Tommaso Allan's first penalty.

Earls then strolled home for the first try, Robbie Henshaw standing up in the tackle and wriggling round to pop the scoring pass inside.

That Ireland had the opportunity at all owed everything to Iain Henderson and Rory Best pulling off a fine choke-tackle turnover on Parisse.

From the scrum Conor Murray grubbered into the corner, Ireland stole the lineout and struck without mercy.

Such efficiency proved in short supply for the rest of the half.

Allan's second penalty brought Italy within four points, before Sexton struck the left-hand upright with a penalty attempt of his own.

Both teams failed to claim a try when punting kickable penalties to the corner, with Ireland the more frustrated not to seize their chance.

Leonardo Sarto was fortunate to escape a yellow card, a penalty deemed sufficient after a dangerous tackle on Dave Kearney.

And at the death of the half, referee Jerome Garces called Italy offside in the defensive line only to blow for half-time rather than the penalty.

Ireland's imprecision in phase play around the ruck edge almost cost them dear at the top of the second half.

Paul O'Connell won a superlative turnover penalty in his own 22 to relieve early pressure that ought to have been the catalyst to Ireland dominance.

Schmidt's men responded as such, only for Murray to lose the ball at the base, allowing Italy to break with pace and verve.

Parisse ghosted into the 13 channel and thought he had sent Furno into the corner.

O'Mahony had other ideas however, eating up ground before enveloping the big Italy lock and forcing him into touch just before he dotted down.

Again Ireland diced with danger, pulling down an Italy maul to allow Allan to post his third penalty and cut Ireland's lead to a solitary point.

Ireland raised the intensity again, if not the precision, the match driven at times by passion alone.

Two quick penalties from Sexton eased the pressure, before another impressive choke-tackle turnover from Henderson.

Still Italy pressed, but Parisse - hardly fit after his calf haematoma - could continue no longer.

Italy know they are not the same without their inspirational captain, but even with Parisse on the sidelines the Azzurri continued to grind away.

O'Mahony's timing may have been perfect to deny Furno his try, but was potentially-damaging in picking up his yellow card.

Just when Ireland expected to pull away, they had to fight the last nine minutes a man light.

Ireland clung on, at times scintillating but more often ragged.

Schmidt's men forced a penalty to the crowd's palpable relief, only for Sexton to drag it wide.

Italy broke again, still refusing to accept there could be no comeback. But then Ireland turned the ball over once more, Sexton punted for touch, and O'Connell and company tiptoed their way to the last eight.